1. Field of the Invention
This invention relates a process for the manufacture of 1,3,3,3-tetrafluoropropene (HFO-1234ze). More particularly, the invention pertains to a process for the manufacture of HFO-1234ze by a two stage process. The process comprises a vapor phase hydrofluorination of 1-chloro-3,3,3-trifluoropropene (HCFC-1233zd) into 1-chloro-1,3,3,3-tetrafluoropropane (HCFC-244fa) and/or 1,1,1,3,3-pentafluoropropane (HFC-245fa), followed by the thermal dehydrochlorination of HCFC-244fa and dehydrofluorination of HFC-245fa in the presence of a catalyst, thus forming a reaction product which comprises 1,3,3,3-tetrafluoropropene.
2. Description of the Related Art
Traditionally, chlorofluorocarbons (CFCs) like trichlorofluoromethane and dichlorodifluoromethane have been used as refrigerants, blowing agents and diluents for gaseous sterilization. In recent years, there has been widespread concern that certain chlorofluorocarbons might be detrimental to the Earth's ozone layer. As a result, there is a worldwide effort to use halocarbons which contain fewer or no chlorine substituents. Accordingly, the production of hydrofluorocarbons, or compounds containing only carbon, hydrogen and fluorine, has been the subject of increasing interest to provide environmentally desirable products for use as solvents, blowing agents, refrigerants, cleaning agents, aerosol propellants, heat transfer media, dielectrics, fire extinguishing compositions and power cycle working fluids. In this regard, 1,3,3,3-tetrafluoropropene (HFO-1234ze) is a compound that has the potential to be used as a zero Ozone Depletion Potential (ODP) and a low Global Warming Potential (GWP) refrigerant, blowing agent, aerosol propellant, solvent, etc, and also as a fluorinated monomer.
It is known in the art to produce HFO-1234ze. For example, U.S. Pat. No. 5,710,352 teaches the fluorination of 1,1,1,3,3-pentachloropropane (HCC-240fa) to form HCFC-1233zd and a small amount of HFO-1234ze. U.S. Pat. No. 5,895,825 teaches the fluorination of HCFC-1233zd to form HFO-1234ze. U.S. Pat. No. 6,472,573 also teaches the fluorination of HCFC-1233zd to form HFO-1234ze. U.S. Pat. No. 6,124,510 teaches the formation of cis and trans isomers of HFO-1234ze by the dehydrofluorination of HFC-245fa using either a strong base or a chromium-based catalyst. Additionally, European patent EP 0939071 describes the formation of HFC-245fa via the fluorination of HCC-240fa through intermediate reaction product which is an azeotropic mixture of HCFC-1233zd and HFO-1234ze.
It has been determined that these known processes are not economical relative to their product yield. Accordingly, the present invention provides an alternate process for forming HFO-1234ze which is more economical than prior art processes and at a higher yield as compared to known processes. In particular, it has now been found that HFO-1234ze may be formed by a two step reaction involving the hydrofluorination of 1-chloro-3,3,3-trifluoropropene (HCFC-1233zd) into 1-chloro-1,3,3,3-tetrafluoropropane (HCFC-244fa) and optionally 1,1,1,3,3-pentafluoropropane (HFC-245fa), followed by the dehydrochlorination of HCFC-244fa and dehydrofluorination of HFC-245fa via thermal decomposition in the presence of a catalyst.